Thermal transfer sheet

ABSTRACT

A thermal transfer sheet is provided that can yield thermally transferred images, which possess excellent various fastness or resistance properties even under severe service conditions, and comprises a transferable protective layer having good transferability. In a thermal transfer sheet comprising a substrate sheet and a thermally transferable protective layer on the substrate sheet, the thermally transferable protective layer comprises a scratch-resistant layer which is repeatedly provided one by one for each picture plane unit in the thermal transfer sheet. An area of the scratch-resistant layer for each picture plane unit is smaller than an area of an object in its transfer surface. By virtue of this construction, at the time of the transfer of a protective layer onto an object, layer cutting does not occur within the scratch-resistant layer but within other layer (such as peel layer or adhesive layer), and, consequently, the protective layer can be transferred with good transferability.

This application is a division of U.S. Ser. No. 10/163,874, filed Jun.7, 2002, now U.S. Pat. No. 6,815,397.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a thermal transfer sheet and anintermediate transfer recording medium that can yield prints havingthermally transferred images, which possess excellent various fastnessor resistance properties even under severe service conditions, and canrealize the transfer of a transfer portion or a protective layer onto anobject with good transferability.

2. Prior Art

Thermal transfer has become extensively used as a simple printingmethod. The thermal transfer is a method which comprises the steps of:putting a thermal transfer sheet, comprising a colorant layer providedon one side of a substrate sheet, on top of a thermal transferimage-receiving sheet optionally provided with an image-receptive layer;and image-wise heating the backside of the thermal transfer sheet byheating means such as a thermal head to selectively transfer thecolorant contained in the colorant layer to form an image on the thermaltransfer image-receiving sheet.

Thermal transfer methods are classified into thermal ink transfer (hotmelt-type thermal transfer) and thermal dye sublimation transfer(sublimation-type thermal transfer). The thermal ink transfer is amethod for image formation wherein a thermal transfer sheet comprising asubstrate sheet, such as a PET film, bearing thereon a hot-melt inklayer, comprising a dispersion of a colorant, such as a pigment, in abinder, such as a hot-melt wax or resin, is provided and energyaccording to image information is applied to heating means such as athermal head to transfer the colorant together with the binder onto athermal transfer image-receiving sheet such as paper or plastic sheets.Images produced by the thermal ink transfer have high density andpossess high sharpness and are suitable for recording binary images ofcharacters or the like.

On the other hand, the thermal dye sublimation transfer is a method forimage formation which comprises the steps of: providing a thermaltransfer sheet comprising a substrate sheet, such as a PET film, bearingthereon a dye layer comprising a dye, which is mainly thermallytransferred by sublimation, dissolved or dispersed in a resin binder;and applying energy according to image information to heating means suchas a thermal head to transfer only the dye onto a thermal transferimage-receiving sheet comprising a substrate sheet, such as paper or aplastic, optionally provided with a dye-receptive layer. The thermal dyesublimation transfer can regulate the amount of the dye transferredaccording to the quantity of energy applied and thus can form gradationimages of which the image density has been regulated dot by dot of thethermal head. Further, since the colorant used is a dye, the formedimage is transparent, and the reproduction of intermediate colorsproduced by superimposing different color dyes on top of each other orone another is excellent. Accordingly, high-quality photograph-like fullcolor images can be formed with excellent reproduction of intermediatecolors by transferring different color dyes, such as yellow, magenta,cyan, and black, onto a thermal transfer image-receiving sheet, so as tosuperimpose the color dyes on top of each other or one another, from athermal transfer sheet of the different colors.

These thermal transfer methods can simply form various images and thushave become utilized in the formation of prints the number of which maybe relatively small. Thermal transfer sheets used with these thermaltransfer methods have various practical applications. Representativeexamples of applications include proof sheets, and recording sheets foroutput images, output plans or designs drawn by CAD/CAM or the like, orimages output from a variety of medical analyzers or measuringinstruments such as CT scanners and endoscopic cameras. They can also beused as the alternative of instant photographs, and as paper forproducing identity certifications, ID cards, credit cards, and othercards on which facial photographs or the like are printed, or forproducing synthetic or memorial photographs which are taken at amusementfacilities such as recreation parks, game centers, museums, aquariumsand the like.

When ID cards such as identity certifications are prepared using theabove thermal transfer sheet, the thermal ink transfer method can easilyform binary images of characters, numerals and the like. The thermal inktransfer method, however, is unsuitable for the formation of imagesrequired to have high quality, such as a photograph of a face. Further,the formed images are disadvantageously poor in fastness or resistanceproperties, particularly abrasion resistance. On the other hand, thethermal dye sublimation transfer is suitable for the formation ofgradation images such as a photograph of a face. Unlike images formedusing printing ink, the images formed by thermal dye sublimationtransfer, however, do not contain any vehicle and thus aredisadvantageously poor in fastness and resistance properties such aslightfastness and weathering resistance.

In order to overcome the above drawbacks, a method has been adoptedwherein a transparent film is laminated onto the surface of the formedimage. This method, however, involves a complicate operation. Inaddition, in this method, since lamination is carried out on the wholeobject, curling occurs in the object. Further, a very thin film cannotbe used for reasons of laminating operation. This inevitably increasesthe thickness of the whole print.

In order to solve these drawbacks, a method has been proposed wherein aprotective layer transfer sheet comprising a substrate film and atransferable resin layer (a protective layer) provided on the substratefilm is provided and the transferable resin layer is transferred toprovide a protective layer on at least a part of the image. According tothis method, fastness or resistance properties such as chemicalresistance and lightfastness can be improved to some extent. Thefastness and resistance properties of the thermally transferred image,however, are not yet satisfactory under severe practical serviceconditions. The protective layer transfer sheet is advantageous in thatthe size of the protective layer (resin layer) transferred can beproperly varied, but on the other hand, a tendency toward an increase inprotective layer transfer processing speed has made it difficult totransfer the protective layer with good transferability. The protectivelayer transfer sheet has many additional disadvantages including that,when the fastness or resistance properties of the protective layer, suchas heat resistance is improved, heat applied at the time of the transferof the protective layer is likely to deteriorate the transferability.

The diversification of the applications has led to a demand for theformation of a thermally transferred image on a desired object. A methodhas been proposed, as one method for meeting this demand, wherein acolorant such as a dye or a pigment is transferred, from a thermaltransfer sheet comprising a dye layer or a hot-melt ink layer, onto areceptive layer in an intermediate transfer recording medium comprisingthe receptive layer separably provided on a substrate to form an imageon the receptive layer and, thereafter, the intermediate transferrecording medium is heated to transfer the receptive layer, with theimage formed thereon, onto an object (Japanese Patent Laid-Open No.238791/1987 or the like).

Since the use of the intermediate transfer recording medium permits thereceptive layer to be transferred onto an object, this method ispreferably used, for example, for objects, onto which a colorant is lesslikely to be transferred making it impossible to form high-qualityimages directly on them, and objects which are likely to be fused to thecolorant layer at the time of thermal transfer. Further, a method may beadopted wherein necessary matter such as a signature is previouslywritten or printed on an object and, thereafter, a transfer portion,with an image of characters, photographs or the like being formedthereon, is transferred from an intermediate transfer recording medium.Therefore, the intermediate transfer recording medium is preferably usedin the preparation of passports or other identity certifications, creditcards/ID cards, or other prints.

The present applicant has proposed in Japanese Patent Laid-Open No.315639/1998 a receptive layer transfer sheet (an intermediate transfermedium film) wherein, in order to impart fastness and resistanceproperties, such as lightfastness, weathering resistance, and abrasionresistance, to thermally transferred images on objects such as ID cards,an ionizing radiation-cured resin layer and a receptive layer areseparably provided on a substrate.

When the above intermediate transfer recording medium is used, thefastness and resistance properties of the thermally transferred imagecan be improved. However, the hardness of the ionizing radiation-curedresin layer is so hard that the ionizing radiation-cured resin layercannot conform to the flexibility of the object, leading to thedeformation of the object between the transfer portion and thenon-transfer portion of the intermediate transfer recording medium.Further, in transferring the intermediate transfer recording medium ontoan object, due to a tendency toward an increase in transfer processingspeed, the transferability of the intermediate transfer recording mediumis unsatisfactory, and, in this case, for example, uneven edge of thetransferred portion or uneven transferred portion, which isdisadvantageous from the practical point of view, occurs.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to solve the aboveproblems of the prior art and to provide a thermal transfer sheet thatcan yield thermally transferred images, which possess excellent variousfastness or resistance properties even under severe service conditions,and comprises a transferable protective layer having goodtransferability.

It is another object of the present invention to provide an intermediatetransfer recording medium, comprising at least a peel layer, a curedproduct of an ionizing radiation-curable resin layer, and a receptivelayer provided in that order on a substrate film, that can yield printshaving a thermally transferred image possessing excellent variousfastness and resistance properties even under severe service conditions,has good transferability, and can prevent the deformation of an objectbetween the transfer portion and the non-transfer portion of theintermediate transfer recording medium, and to provide a print.

The above object can be attained by a first thermal transfer sheetaccording to the present invention, comprising a substrate sheet and athermally transferable protective layer provided on the substrate sheet,wherein the thermally transferable protective layer comprises ascratch-resistant layer; the scratch-resistant layer is repeatedlyprovided one by one for each picture plane unit in the thermal transfersheet; and an area of the scratch-resistant layer for each picture planeunit is smaller than an area of an object in its transfer surface. Inother words, the area of the object in its transfer surface can also besaid to be the size of the outward form of the protective layer formedby the transfer of the thermally transferable protective layer onto theobject. The thermally transferable protective layer preferably comprisesa peel layer, the scratch-resistant layer, and an adhesive layerprovided in that order as viewed from the substrate sheet side.According to this construction, at the time of the transfer of aprotective layer onto an object, layer cutting does not occur within thescratch-resistant layer but within other layer (such as peel layer oradhesive layer), and, consequently, the protective layer can betransferred with good transferability.

The scratch-resistant layer is preferably formed from an ionizingradiation-curable resin. Upon exposure to an ultraviolet light or anelectron beam, an ionizing radiation-curable resin layer causescrosslinking to form a scratch-resistant layer having athree-dimensional network structure which is strong and possessesexcellent various fastness and resistance properties. Further, theprotective layer is not cut within the scratch-resistant layer butwithin the peel layer or adhesive layer having good transferability andis transferred onto an object. The use of the thermal transfer sheetaccording to the present invention can realize excellent variousfastness and resistance properties of thermally transferred images andgood transferability in the transfer of a protective layer onto anobject even under severe service conditions.

The second thermal transfer sheet according to the present inventioncomprises a substrate sheet and a thermally transferable protectivelayer provided on the substrate sheet, wherein the thermallytransferable protective layer comprises at least a peel layer, a thermaltransfer resin layer, and an adhesive layer provided in that order asviewed from the substrate sheet side, and the thermal transfer resinlayer comprises a cured product of an ionizing radiation-curable resin.According to this construction, in the formation of the thermal transferresin layer, upon exposure to ultraviolet light or electron beam, theionizing radiation-curable resin layer causes crosslinking and forms athree-dimensional network structure which is strong and possessesexcellent various fastness and resistance properties. In the thermaltransfer sheet according to the present invention, in order to ensurethe fixation of the protective layer onto the object, an adhesive layeris provided on the thermal transfer resin layer, and, in addition, apeel layer is provided between the substrate sheet and the thermaltransfer resin layer so that, in the transfer of the protective layeronto the object, the protective layer is faithfully separated from thesubstrate sheet (that is, so that uneven transfer of the protectivelayer can be avoided). The use of this thermal transfer sheet canrealize excellent various fastness and resistance properties ofthermally transferred images and good transferability of the protectivelayer onto the object even under severe service conditions.

In the thermal transfer sheet according to the present invention,preferably, a thermally transferable colorant layer(s) for at least onecolor is provided on the substrate sheet, the thermally transferableprotective layer is then provided on the substrate sheet so that thethermally transferable colorant layer and the thermally transferableprotective layer constitute one picture plane unit, and a combination ofthe thermally transferable colorant layer with the thermallytransferable protective layer is repeatedly provided in a face serialmanner for constituting each picture plane unit. In this case, there isno need to provide two thermal transfer sheets, i.e., a thermal transfersheet for transferring a protective layer and a thermal transfer sheetfor forming a thermally transferred image, and the provision of only onethermal transfer sheet suffices for the formation of a thermallytransferred image and the transfer of a protective layer. Thus, theefficiency is very high, and, in addition, the production cost of athermal transfer sheet can be reduced.

The ionizing radiation-curable resin is preferably a urethane-modifiedacrylic base resin, and, particularly preferably, 5 to 40 parts byweight, based on 100 parts by weight of the urethane-modified acrylicbase resin, of an oligomer is contained. In this case, the protectivelayer is flexible, and, in addition, prints having a thermallytransferred image can be obtained which possess excellent fastness andresistance properties such as excellent chemical resistance,lightfastness, and weathering resistance.

According to the present invention, there is provided an intermediatetransfer recording medium comprising a substrate film and a transferportion provided on the substrate film, wherein said transfer portioncomprises at least a peel layer, a cured product of an ionizingradiation-curable resin layer, and a receptive layer provided in thatorder as viewed from the substrate film side, and the ionizingradiation-curable resin layer comprises an urethane-modified acrylicbase resin. Upon exposure to ultraviolet light or electron beam, theionizing radiation-curable resin layer causes crosslinking to form anionizing radiation-cured resin layer having a three-dimensional networkstructure which is strong and possesses excellent various fastness andresistance properties. In the ionizing radiation-curable resin layer,particularly preferably, 5 to 40 parts by weight, based on 100 parts byweight, of the urethane-modified acrylic base resin, of an oligomer iscontained. In this case, the protective layer transferred onto theobject is highly flexible, and the deformation of an object between thetransfer portion and the non-transfer portion of the intermediatetransfer recording medium can be prevented. This is consideredattributable to a difference in shrinkage between the transfer portionand the non-transfer portion.

In the intermediate transfer recording medium according to the presentinvention, at least a peel layer, a cured product of an ionizingradiation-curable resin layer, and a receptive layer are provided inthat order on a substrate film to constitute a transfer portion. Thetransfer portion can be transferred onto an object without any uneventransfer and with even edge of the transferred portion, that is, withgood transferability.

Further, according to the present invention, there is provided a printproduced by providing the above intermediate transfer recording medium,wherein the print is obtained by the steps of forming a thermal transferimage on the intermediate transfer recording medium in its transferportion, and transferring the transfer portion with the image formedthereon onto an object.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic cross-sectional view showing an embodiment of thefirst thermal transfer sheet according to the present invention;

FIG. 1B is a schematic plan view showing another embodiment of the firstthermal transfer sheet according to the present invention;

FIG. 1C is a schematic explanatory view showing an embodiment wherein aprotective layer is thermally transferred onto an object using the firstthermal transfer sheet according to the present invention;

FIG. 1D is a schematic cross-sectional view showing an assembly afterthe transfer of a thermally transferable protective layer, using thefirst thermal transfer sheet according to the present invention, onto anobject with a thermally transferred image formed thereon;

FIG. 2A is a schematic cross-sectional view showing an embodiment of thesecond thermal transfer sheet according to the present invention;

FIG. 2B is a schematic plan view showing another embodiment of thesecond thermal transfer sheet according to the present invention;

FIG. 2C is a schematic explanatory view showing an embodiment wherein aprotective layer is thermally transferred onto an object using thesecond thermal transfer sheet according to the present invention;

FIG. 2D is a schematic cross-sectional view showing an assembly afterthe transfer of a thermally transferable protective layer, using thesecond thermal transfer sheet according to the present invention, ontoan object with a thermally transferred image formed thereon;

FIG. 3A is a cross-sectional view showing one embodiment of theintermediate transfer recording medium according to the presentinvention; and

FIG. 3B is a cross-sectional view showing one embodiment of the printaccording to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The first thermal transfer sheet according to the present invention willbe explained with reference to the accompanying drawings.

FIG. 1A is a schematic cross-sectional view showing one embodiment ofthe first thermal transfer sheet 101 according to the present invention.In the first thermal transfer sheet 101, a peel layer 103, ascratch-resistant layer 104, and an adhesive layer 105 are provided inthat order on a substrate sheet 102. In this case, three layers of thepeel layer 103, the scratch-resistant layer 104, and the adhesive layer105 provided on the substrate sheet 102 constitute a thermallytransferable protective layer 106. That is, the thermally transferableprotective layer 106 is constituted by the scratch-resistant layer 104and other layers, i.e., the peel layer 103 and the adhesive layer 105.At the same time, in the thermal transfer sheet 101, thescratch-resistant layer 104 is repeatedly provided one by one on thesubstrate sheet 102 for each picture plane unit. In this case, the sizeof the scratch-resistant layer 104 is smaller than the size A of anobject in its transfer surface. By virtue of this construction, at thetime of the transfer of the protective layer 106 onto an object, layercutting does not occur in the scratch-resistant layer 104 but within theadhesive layer 105 (and the peel layer 103), and, consequently, theprotective layer can be transferred with good transferability. Aheat-resistant slip layer (not shown) can be provided on the substratesheet 102 in its surface remote from the thermally transferableprotective layer 106 from the viewpoint of preventing sticking, cocklingand other unfavorable phenomena caused by heat of a thermal head, a heatroll or the like.

FIG. 1B is a schematic plan view showing another embodiment of the firstthermal transfer sheet 101 according to the present invention. In thisembodiment, thermally transferable colorant layers 107 of yellow (Y),magenta (M), and cyan (C) are provided on a substrate sheet 102 and athermally transferable protective layer 106 is then provided on thesubstrate sheet 102. One unit (U) of a combination of the thermallytransferable colorant layers 107 with the thermally transferableprotective layer 106 is then repeatedly provided in a face serialmanner. The thermally transferable protective layer comprises at least ascratch-resistant layer and other layers, although these layers are notshown because the drawing is not a cross-sectional view but a plan view.

FIG. 1C is a schematic explanatory view showing an embodiment wherein aprotective layer 106 is thermally transferred onto an object 108 usingthe first thermal transfer sheet 101 according to the present invention.In this embodiment, thermally transferable colorant layers 107 of atleast three colors of yellow, magenta, and cyan are provided on asubstrate sheet 102, and a thermally transferable protective layer 106is then provided on the substrate sheet 102. One unit of a combinationof the thermally transferable colorant layers 107 with the thermallytransferable protective layer 106 is repeatedly formed in a face serialmanner to form the thermal transfer sheet 101. The thermal transfersheet 101 is used to thermally transfer the colorant layer 107 in thethermal transfer sheet 101 onto the object 108 by means of a thermalhead 110 to form an image 109. The protective layer 106 is thermallytransferred by the thermal head 110 from the thermal transfer sheet 101onto the image 109 so as to cover at least the printed portion, and thesubstrate sheet 102 is then separated from the object 108. Although thelayer construction of the thermally transferable protective layer is notshown, the scratch-resistant layer has a size smaller than the size ofthe protective layer 106 thermally transferred onto the object 108 andcovers the printed image.

FIG. 1D is a schematic cross-sectional view showing an assembly afterthe transfer of a thermally transferable protective layer, using thefirst thermal transfer sheet according to the present invention, onto anobject with a thermally transferred image formed thereon.

A receptive layer 112 is previously formed on an object 108, and athermally transferred image 109 is then formed on the receptive layerusing a thermal transfer sheet comprising thermally transferablecolorant layers provided on a substrate. Thereafter, a protective layer106 is transferred using the thermal transfer sheet according to thepresent invention provided with the thermally transferable protectivelayer 106 so as to cover the thermally transferred image 109. Theadhesive layer 105 is transferred onto a portion which comes intocontact with the thermally transferred image 109, and thescratch-resistant layer 104 is stacked onto the adhesive layer 105 sothat the size of the scratch-resistant layer 104 is smaller than thesize of the transferred adhesive layer 105.

Thermal Transfer Sheet

Substrate Sheet:

In the thermal transfer sheet according to the present invention, anysubstrate sheet used in conventional thermal transfer sheets may be usedso far as the substrate sheet has some level of heat resistance andstrength, and examples thereof include tissue papers, such as glassinepaper, capacitor paper, and paraffin paper; and films of plastics, forexample, polyesters, such as polyethylene terephthalate and polyethylenenaphthalate, polypropylene, cellophane, polycarbonate, celluloseacetate, polyethylene, polyvinyl chloride, polystyrene, nylon,polyimide, polyvinylidene chloride, and ionomers. The thickness of thesubstrate sheet may be properly varied depending upon materials for thesubstrate sheet so that the substrate sheet has proper strength, heatresistance and other properties. However, the thickness is 2 to 100 μm,preferably about 10 to 80 μm.

In order to regulate the surface gloss of the print after the transferof the protective layer, a matte polyethylene terephthalate film may beused as the substrate sheet. Sandblasting, incorporation, internalfoaming and the like may be mentioned as means for matting.

Peel Layer:

In the thermal transfer sheet according to the present invention, thescratch-resistant layer is preferably provided on the substrate sheetthrough a peel layer 103. The provision of the peel layer permits thescratch-resistant layer to be surely and easily transferred from thethermal transfer sheet onto an object.

The peel layer may comprise, for example, waxes, such asmicrocrystalline wax, carnauba wax, paraffin wax, Fischer-Tropsh wax,various types of low-molecular weight polyethylene, Japan wax, beeswax,spermaceti, insect wax, wool wax, shellac wax, candelilla wax,petrolactum, partially modified wax, fatty esters, and fatty amides, andthermoplastic resins, such as silicone wax, silicone resin, fluororesin,acrylic resin, polyester resin, polyurethane resin, cellulose resin,vinyl chloride-vinyl acetate copolymer, and nitrocellulose.

Further, the peel layer may comprise a binder resin and a releasablematerial. Binder resins usable herein include thermoplastic resins, forexample, acrylic resins, such as polymethyl methacrylate, polyethylmethacrylate, polybutyl acrylate, vinyl resins, such as polyvinylacetate, vinyl chloride-vinyl acetate copolymer, polyvinyl alcohol, andpolyvinylbutyral, and cellulose derivatives, such as ethylcellulose,nitrocellulose, and cellulose acetate, and thermosetting resins, forexample, unsaturated polyester resins, polyester resins, polyurethaneresins, and aminoalkyd resins. Releasable materials include waxes,silicone wax, silicone resins, melamine resins, fluororesins, finepowders of talc or silica, and lubricants such as surfactants or metalsoaps.

The peel layer may be formed by dissolving or dispersing theabove-described necessary materials in a suitable solvent to prepare acoating liquid for a peel layer, coating the coating liquid onto asubstrate sheet by gravure printing, screen printing, reverse coatingusing a gravure plate or other means, and drying the coating. Thecoverage is generally 0.1 to 10 g/m² on a dry basis.

Scratch-Resistant Layer:

The first thermal transfer sheet according to the present inventioncomprises a substrate sheet and, provided on the substrate sheet, atleast a scratch-resistant layer and other layers which constitute athermally transferable protective layer.

In the thermally transferable protective layer, the scratch-resistantlayer 104 mainly functions to impart various fastness and resistanceproperties to thermally transferred images. This scratch-resistant layerpreferably comprises a cured product of an ionizing radiation-curableresin and will be specifically described below.

A composition prepared by properly mixing prepolymers, oligomers and/ormonomers containing, in the molecule thereof, polymerizalbe unsaturatedbonds, such as (meth)acryloyl and (meth)acryloyloxy groups((meth)acryloyl referring to acryloyl or methacryloyl; for (meth), thesame shall apply hereinafter) or epoxy group together may be mentionedas the ionizing radiation-curable resin. Prepolymers and oligomersinclude acrylates, such as urethane(meth)acrylate,polyester(meth)acrylate, and epoxy(meth)acrylate, silicone resins suchas siloxane, and unsaturated polyesters, and epoxy.

Examples of monomers include styrene monomers such as styrene andα-methylstyrene, methyl(meth)acrylate, (meth)acrylic acid-2-ethylhexyl,dipentaerythritol hexa(meth)acrylate, dipentaerythritolpenta(meth)-acrylate, trimethylolpropane tri(meth)acrylate, and/orpolyol compounds containing, in the molecule thereof, two or more thiolgroups, for example, trimethyolpropane trithioglycolate,trimethyolpropane trithiopropylate, and pentaerythritol tetrathioglycol.One of or a mixture of two or more of the above compounds is usedaccording to need. In order to impart ordinary coatability to the resincomposition, the resin composition preferably comprises not less than 5%by weight of the prepolymer or the oligomer and not more than 95% byweight of the monomer and/or polythiol.

In the selection of the monomer, when the cured product is required tobe flexible, a structure having a relatively low degree of crosslinkingis adopted by bringing the amount of the monomer to a relatively smallone or using a monofunctional or bifuctional acrylate monomer withcaution so as not to sacrifice various fastness and resistanceproperties of the scratch-resistant layer and the coatability.

For example, when the cured product is required to be heat resistant,hard, or resistant to solvents, a structure having a high degree ofcrosslinking is preferably adopted by bringing the amount of the monomerto a relatively large one with caution so as not to sacrifice thecoatability or using a tri- or higher functional acrylate monomer. Amethod may also be used wherein a monofunctional or bifunctional monomeris mixed with a tri- or higher functional monomer to regulatecoatability and properties of the cured product.

Monofunctional acrylate monomers include 2-hydroxy acrylate, 2-hexylacrylate, and phenoxyethyl acrylate. Bifunctional acrylate monomersinclude ethylene glycol diacrylate and 1,6-hexanediol diacrylate, andtri- or higher functional acrylate monomers include trimethylol propanetriacrylate, pentaerythritol hexaacrylate, and dipentaerythritolhexaacrylate.

A mixture of at least one of the above prepolymers, oligomers, andmonomers with about 1 to 50% by weight of the following ionizingradiation-non-curable resin may be used from the viewpoint of regulatingproperties of the cured product such as flexibility and surfacehardness. Ionizing radiation-non-curable resins include urethane,cellulosic, polyester, acrylic, butyral, polyvinyl chloride, polyvinylacetate and other thermoplastic resins.

The scratch-resistant layer of the thermal transfer sheet according tothe present invention has excellent various fastness and resistanceproperties and a suitable level of flexibility, which affectshandleability, appearance, etc. of prints after transfer, and thus ispreferably formed from a urethane-modified acrylic base resin as anionizing radiation-curable resin. Further, the use of an ionizingradiation-curable resin comprising the urethane-modified acrylic baseresin and 5 to 40 parts by weight, based on 100 parts by weight of theurethane-modified acrylic base resin, of an oligomer is suitable.

The urethane-modified acrylic base resin contains a urethane bondtherein produced as a result of a reaction of a hydroxyl group (—OH)present in the acrylic resin with an isocyanate (—NCO), and, preferably,5 to 40 parts by weight of an oligomer is contained based on 100 partsby weight of the urethane-modified acrylic base resin. This can impartan excellent function, i.e., a combination of flexibility with fastnessand resistance properties, to the protective layer. Regarding theadditive to the urethane-modified acrylic base resin, in addition to theoligomer, monomers may also be of course added. When the amount of theoligomer used is small, the strength, fastness and resistance propertiesand other properties of the resin layer are unsatisfactory. On the otherhand, when the amount of the oligomer used is excessively large, thetackiness of the surface of the resin layer is so high that, forexample, blocking is disadvantageously likely to occur.

When the ionizing radiation-curable resin is cured by ionizing radiationirradiation, a transparent resin should be used. Photopolymerizationinitiators, such as acetophenones, benzophenones, Michler's benzoylbenzoate, α-amyloxime ester, tetramethylthiuram monosulfide, andthioxanthones, and/or photosensitizers, such as n-butylamine,triethylamine, and tri-n-butylphosphine, may be incorporated into theionizing radiation-curable resin composition. Further, preferably,silicone resins, waxes, fluororesins, melanine resins, surfactants orthe like is incorporated from the viewpoint of releasability.

In the present invention, ultraviolet light is mainly used for fullycuring the thermal transfer resin layer comprising the ionizingradiation-curable resin-containing resin composition on the substratesheet. However, among electromagnetic radiations or charged particlebeams, visible light, γ radiation, and X radiation, which are ionizingradiations having energy quantum capable of polymerizing or crosslinkingmolecules, are also usable.

An ultraviolet irradiation device is generally used as an ionizingradiation irradiation device. Ultrahigh-pressure mercury lamp,high-pressure mercury lamp, low-pressure mercury lamp, carbon arc,blacklight, a metal halide lamp and other light sources are usable asthe ultraviolet irradiation device. Electrons having an energy of 100 to1000 KeV, preferably 100 to 300 KeV, are applied from the device. Theexposure is generally about 5 to 300 KGy (kilogray).

The scratch-resistant layer may be formed by dissolving or dispersing acomposition containing an ionizing radiation-curable resin for thescratch-resistant layer in a suitable solvent to prepare an ink for athermal transfer resin layer, coating the ink onto the substrate sheetby coating means, such as gravure printing, screen printing, or reversecoating using a gravure plate, and drying the coating.

The scratch-resistant layer may be formed in any desired thickness onthe substrate sheet. The thickness, however, is 0.1 to 50 g/m²,preferably about 1 to 20 g/m², on a dry basis.

Adhesive Layer:

An adhesive layer 105 may be provided on the surface of the thermallytransferable protective layer in the thermal transfer sheet according tothe present invention from the viewpoint of improving thetransferability and adhesion to prints as the object. The adhesive layermay comprise any of conventional pressure-sensitive adhesives orheat-sensitive adhesives, preferably comprise a thermoplastic resinhaving a glass transition temperature (Tg) of 50° C. to 80° C.Preferably, for example, a resin having a suitable glass transitiontemperature is selected from resins having good thermal adhesion, suchas polyester resins, vinyl chloride-vinyl acetate copolymer resins,acrylic resins, butyral resins, epoxy resins, polyamide resins, andvinyl chloride resins. The above resin preferably has low molecularweight from the viewpoint of adhesion or when the adhesive layer isformed as a pattern on a part of the thermally transferable protectivelayer, rather than the whole area of the thermally transferableprotective layer, by heating means such as a thermal head.

A coating liquid prepared by optionally adding additives such asinorganic or organic fillers to the above resin for the adhesive layeris coated by the same coating means as used in the formation of thethermal transfer resin layer, and the coating is then dried to form anadhesive layer preferably at a coverage of about 0.5 to 10 g/m² on a drybasis.

In the first thermal transfer sheet according to the present invention,an antistatic layer may be provided on the outermost surface of thethermal transfer sheet on its side where the thermally transferableprotective layer is provided, or on the outermost surface of the thermaltransfer sheet in its side remote from the thermally transferableprotective layer, or on the outermost surface of the thermal transfersheet on its both sides. The antistatic layer may be formed bydissolving or dispersing an antistatic agent, such as a fatty ester, asulfuric ester, a phosphoric ester, an amide, a quaternary ammoniumsalt, a betaine, an amino acid, an acrylic resin, or an ethylene oxideadduct, in a solvent to prepare a solution or a dispersion and coatingthe solution or the dispersion. Means for the formation of theantistatic layer may be the same as described above in connection withthe formation of the scratch-resistant layer. The coverage of theantistatic layer is preferably 0.001 to 0.1 g/m² on a dry basis.

An intermediate layer comprising various resins may be provided betweenthe peel layer and the scratch-resistant layer or between thescratch-resistant layer and the adhesive layer. The intermediate layeris preferably transparent so that the thermally transferred image can beseen through the intermediate layer. Excellent function can be added tothe thermal transfer sheet by imparting various functions to theintermediate layer. For example, resins having high level of elasticdeformation or plastic deformation, for example, polyolefin resin, vinylcopolymer resin, polyurethane resin, and polyamide resin, may be used asresins for imparting cushioning properties. Further, in order to impartantistatic capability to the intermediate layer, the intermediate layermay be formed by adding the above antistatic agent to the resin forimparting cushioning properties, dissolving or dispersing the mixture ina solvent to prepare a solution or a dispersion, and coating thesolution or the dispersion.

Next, the second thermal transfer sheet according to the presentinvention will be explained.

FIG. 2A is a schematic cross-sectional view showing one embodiment ofthe second thermal transfer sheet 101 according to the presentinvention. In this embodiment, a peel layer 103, a thermal transferresin layer 204, and an adhesive layer 105 are provided in that order ona substrate sheet 102. In this case, three layers of the peel layer 103,the thermal transfer resin layer 204, and the adhesive layer 105provided on the substrate sheet 102 constitute a thermally transferableprotective layer 106. The thermal transfer resin layer 104 comprises acured product of an ionizing radiation-curable resin. A heat-resistantslip layer (not shown) can be provided on the substrate sheet 102 in itssurface remote from the thermally transferable protective layer 106 fromthe viewpoint of preventing sticking, cockling and other unfavorablephenomena caused by heat of a thermal head, a heat roll or the like.

FIG. 2B is a schematic plan view showing an embodiment of the secondthermal transfer sheet 101 according to the present invention. In thisembodiment, thermally transferable colorant layers 107 of yellow (Y)magenta (M), and cyan (C) are provided on a substrate sheet and athermally transferable protective layer 106 is then provided on thesubstrate sheet. One unit (U) of a combination of the thermallytransferable colorant layers 107 with the thermally transferableprotective layer 106 is then repeatedly provided in a face serialmanner. The thermally transferable protective layer comprises at least apeel layer, a thermal transfer resin layer, and an adhesive layer,although these layers are not shown because the drawing is not across-sectional view but a plan view.

FIG. 2C is a schematic explanatory view showing an embodiment wherein aprotective layer 106 is thermally transferred onto an object 108 usingthe second thermal transfer sheet 101 according to one embodiment of thepresent invention. In this case, thermally transferable colorant layers107 of at least three colors of yellow, magenta, and cyan are providedon a substrate sheet 102, and a thermally transferable protective layer106 is then provided on the substrate sheet 102. One unit of acombination of the thermally transferable colorant layers 107 with thethermally transferable protective layer 106 is repeatedly formed in aface serial manner to form the thermal transfer sheet 101. The thermaltransfer sheet 101 is used to thermally transfer the colorant layer 107in the thermal transfer sheet 101 onto the object 108 by means of athermal head 110 to form an image 109. The protective layer 106 isthermally transferred by the thermal head 110 from the thermal transfersheet 101 onto the image 109 so as to cover at least the printedportion, and the substrate sheet 102 is then separated from the object108.

FIG. 2D is a schematic cross-sectional view showing an assembly afterthe transfer of a thermally transferable protective layer, using thesecond thermal transfer sheet according to the present invention, ontoan object with a thermally transferred image formed thereon.

A receptive layer 112 is previously formed on an object 108, and athermally transferred image 109 is then formed on the receptive layerusing a thermal transfer sheet comprising thermally transferablecolorant layers provided on a substrate. Thereafter, a protective layer106 is transferred using the thermal transfer sheet according to thepresent invention provided with the thermally transferable protectivelayer 106 so as to cover the thermally transferred image 109. Theadhesive layer 105 is transferred onto a portion which comes intocontact with the thermally transferred image 109, and thescratch-resistant layer 104 is stacked onto the adhesive layer 105 sothat the size of the scratch-resistant layer 104 is smaller than thesize of the transferred adhesive layer 105.

The substrate sheet constituting the second thermal transfer sheetaccording to the present invention may be the same as that used in thefirst thermal transfer sheet.

In the second thermal transfer sheet according to the present invention,a thermal transfer resin layer is provided on the substrate sheetthrough the peel layer 103. The provision of the peel layer permits thethermal transfer resin layer and the adhesive layer provided on theresin layer to be surely and easily transferred from the thermaltransfer sheet onto an object. The peel layer may be the same as thatused in the first thermal transfer sheet.

The second thermal transfer sheet according to the present inventioncomprises a substrate sheet and, provided on the substrate sheet, atleast a peel layer, a thermal transfer resin layer, and an adhesivelayer in that order. At least three layers of the peel layer, thethermal transfer resin layer, and the adhesive layer constitute thethermally transferable protective layer.

In the thermally transferable protective layer, the thermal transferresin layer 204 mainly functions to impart various fastness andresistance properties to thermally transferred images. This thermaltransfer resin layer may comprise a cured product of an ionizingradiation-curable resin which may be the same as that used in the firstthermal transfer sheet. The ionizing radiation-curable resin may becured in the same manner as described above.

The thermal transfer resin layer may be formed by dissolving ordispersing a composition containing the ionizing radiation-curable resinfor the thermal transfer resin layer in a suitable solvent to prepare anink for the formation of a thermal transfer resin layer, coating the inkonto the substrate sheet by coating means, such as gravure printing,screen printing, or reverse coating using a gravure plate, and dryingthe coating.

The thermal transfer resin layer may be formed in any desired thicknesson the substrate sheet. The thickness, however, is 0.1 to 50 g/m²,preferably about 1 to 20 g/m², on a dry basis.

The adhesive layer 5 constituting the thermally transferable protectivelayer in the thermal transfer sheet according to the present inventionfunctions to impart good transferability and adhesion onto prints asobjects to the surface of the thermally transferable protective layer.This adhesive layer may be the same as that used in the first thermaltransfer sheet.

The second thermal transfer sheet according to the present inventioncomprises at least a substrate sheet, a peel layer, a thermal transferresin layer, and an adhesive layer. An antistatic layer may be providedon the surface of the adhesive layer, on the backside of the substratesheet, or on the outermost surface of the thermal transfer sheet in itsboth sides. The antistatic layer may be the same as that used in thefirst thermal transfer sheet.

Further, an intermediate layer comprising various resins may be providedbetween the peel layer and the thermal transfer resin layer or betweenthe thermal transfer resin layer and the adhesive layer. Theintermediate layer is preferably transparent so that the thermallytransferred image can be seen through the intermediate layer. Excellentfunction can be added to the thermal transfer sheet by imparting variousfunctions to the intermediate layer. The intermediate layer may be thesame as that used in the first thermal transfer sheet.

In the first and second thermal transfer sheets according to the presentinvention, if necessary, a heat-resistant slip layer may be provided onthe backside of the substrate sheet, that is, on the surface of thesubstrate sheet remote from the thermally transferable protective layer,from the viewpoint of preventing sticking, cockling and otherunfavorable phenomena caused by heat of thermal transfer means such as athermal head or a heat roll.

Any conventional resin may be used as the resin for constituting theheat-resistant slip layer, and examples thereof include polyvinylbutyral resins, polyvinyl acetoacetal resins, polyester resins, vinylchloride-vinyl acetate copolymers, polyether resins, polybutadieneresins, styrene-butadiene copolymers, acrylic polyols, polyurethaneacrylates, polyester acrylates, polyether acrylates, epoxy acrylates,prepolymers of urethane or epoxy, nitrocellulose resins, cellulosenitrate resins, cellulose acetopropionate resins, cellulose acetatebutyrate resins, cellulose acetate hydrodiene phthalate resins,cellulose acetate resins, aromatic polyamide resins, polyimide resins,polycarbonate resins, chlorinated polyolefin resins, and chlorinatedpolyolefin resins.

Slipperiness-imparting agents added to or topcoated on theheat-resistant slip layer comprising the above resin include phosphoricesters, silicone oils, graphite powder, silicone graft polymers, fluorograft polymers, acrylsilicone graft polymers, acrylsiloxanes,arylsiloxanes, and other silicone polymers. Preferred a layer comprisesa polyol, for example, a high-molecular polyalochol compound, apolyisocyanate compound and a phosphoric ester compound. Further, theaddition of a filler is more preferred.

The heat-resistant slip layer may be formed by dissolving or dispersingthe resin, the slipperiness-imparting agent, and a filler in a suitablesolvent to prepare an ink for the formation of a heat-resistant sliplayer, coating the ink onto the backside of the substrate sheet bycoating means, such as gravure printing, screen printing, or reversecoating using a gravure plate, and drying the coating.

Thermally Transferable Colorant Layer:

The thermally transferable colorant layer 7 provided on the substratesheet in the thermal transfer sheet according to the present inventionmay be either a dye layer comprising a solution or dispersion of a dye,which is mainly thermally transferred by sublimation, in a resin binder,or a heat-fusion ink layer comprising a dispersion of a colorant such asa pigment or a dye in a binder such as heat-fusion wax or resin.Further, a method may also be used wherein, for example, colorant layersof yellow, magenta, and cyan as sublimable dye layers and a heat-fusionink layer as a black color layer are provided in combination in a faceserial manner.

The dye layer as the thermally transferable colorant layer is a layercomprising a dye supported by a proper binder resin. Dyes commonly usedin conventional thermal transfer sheets may be effectively used withoutparticular limitation. For example, MS Red G, Macrolex Red Violet R,Ceres Red 7B, Samaron Red HBSL, and Resolin Red F 3BS may be mentionedas several examples of magenta dyes. Phorone Brilliant Yellow 6 GL,PTY-52, Macrolex Yellow 6G and the like may be mentioned as yellow dyes.Kayaset Blue 714, Waxoline Blue AP-FW, Phorone Brilliant Blue S-R, andMS Blue 100 may be mentioned as cyan dyes.

Any conventional binder resin may be used for carrying the above dyes,and examples of preferred binder resins include: cellulosic resins suchas ethylcellulose, hydroxyethylcellulose, ethylhydroxycellulose,hydroxypropylcellulose, methylcellulose, cellulose acetate, andcellulose acetate butyrate; vinyl resins such as polyvinyl alcohol,polyvinyl acetate, polyvinyl butyral, polyvinyl acetal, polyvinylpyrrolidone, and polyacrylamide; and polyesters. Among them, forexample, cellulosic, acetal, butyral, and polyester resins are preferredfrom the viewpoints of heat resistance, transferability of dyes and thelike. Further, if necessary, various conventional other additives may beincorporated into the dye layer.

Dye layers are preferably formed by adding the sublimable dye, thebinder resin and other optional ingredients to a suitable solvent todissolve or disperse the ingredients in the solvent to prepare coatingmaterials or inks for the formation of dye layers, coating the coatingmaterials or the inks in a face serial manner on the substrate film, anddrying the coatings. The coverage of the dye layer is about 0.2 to 5.0g/m², preferably about 0.4 to 2.0 g/m², on a dry basis. The content ofthe sublimable dye in the dye layer is suitably 5 to 90% by weight,preferably 10 to 70% by weight, based on the dye layer.

The heat-fusion ink layer as the thermally transferable colorant layercomprises a colorant, a binder and optional desired additives. Amongorganic or inorganic pigments or dyes, those having good properties as arecording material, for example, those, which have satisfactory colordensity and are less likely to cause color change and fading uponexposure to light, heat, and temperature, are preferred as the colorant.Colorants having black, cyan, magenta, yellow, and other hues areusable. The binder used is composed mainly of wax and further comprisesa mixture of a drying oil, a resin, a mineral oil, cellulose, and arubber derivative.

Waxes include microcrystalline wax, carnauba wax, and paraffin wax.Further, other various waxes such as Fischer-Tropsh wax, various typesof low-molecular weight polyethylene, Japan wax, beeswax, spermaceti,insect wax, wool wax, shellac wax, candelilla wax, petrolactum,polyester wax, partially modified wax, fatty esters, and fatty amidesmay also be used. A vinyl chloride-vinyl acetate copolymer resin, anacrylic resin, or a combination of an acrylic resin with a chlorinatedrubber, a vinyl chloride-vinyl acetate copolymer resin, a cellulosicresin or the like may be used as the binder used in the heat-fusion inklayer.

The heat-fusion ink layer may be formed at a coverage of about 1 to 8g/m² on a dry basis, for example, by hot melt coating, hot lacquercoating, gravure coating, gravure reverse coating, knife coating, aircoating, or roll coating a composition for a heat-fusion ink layercomprising the colorant, the binder and optional additives.

An image formation method for providing a print, which comprises animage thermally transferred onto an object and a protective layertransferred onto the image, using the thermal transfer sheet accordingto the present invention will be described.

A thermal transfer sheet comprising a thermally transferable colorantlayer provided on a substrate sheet is first provided. A colorant isthermally transferred from the colorant layer onto an object to form animage. Next, a protective layer is thermally transferred from a thermaltransfer sheet, comprising a thermally transferable protective layerprovided separably on the substrate sheet, onto the image so as to coverat least the printed portion, and the substrate sheet is then separated.

In the thermal transfer recording method used for forming an image on anobject, recording is carried out by generating thermal energy controlledby image signals by means of a thermal head and using the thermal energyas energy for activating a recording material such as ink. In this case,a thermal transfer sheet comprising a thermally transferable colorantlayer provided on a substrate sheet is put on top of recording paper.The laminate is passed through between a thermal head and a platen whichare under a suitable applied pressure. The thermal head of which thetemperature has been raised by energization activates the recordingmaterial, and an image is transferred onto the recording paper with theaid of the pressure of the platen.

Thermal transfer recording methods are classified into thermal dyesublimation transfer (sublimation-type thermal transfer) and thermal inktransfer (hot melt-type thermal transfer). Any of these methods may beused in the formation of an image in the print according to the presentinvention. A method may also be adopted wherein a combination of, thethermal dye sublimation transfer with the thermal ink transfer is usedin such a manner that, for example, a gradation image portion is formedby the thermal dye sublimation transfer recording while a characterportion is formed by the thermal ink transfer recording.

The thermal transfer recording may also be carried out by thermaltransfer means, wherein heating is carried out by laser beamirradiation, in addition to the above thermal head method.

Further, in the present invention, examples of means usable for thethermal transfer of the protective layer include: a method wherein aprint and a thermal transfer sheet comprising a thermally transferableprotective layer provided on a substrate sheet are sandwiched betweenthe thermal head and the platen and heating is carried out from thethermal head; a heat roll method which is adopted in many ofcommercially available laminators and performs hot pressing by means ofa pair of heat rolls; a method wherein the print and the thermaltransfer sheet are sandwiched between heated flat plates or between aheated flat plate and a roll and, in this state, hot pressing is carriedout; and a thermal transfer method using laser irradiation for heating.

When a thermal head is used as the thermal transfer means for theprotective layer, the same thermal head as used in the formation of theimage may be used, or alternatively a thermal head different from thatused in the formation of the image may be used. Preferably, however,from the viewpoint of efficiency, a method is used wherein a thermaltransfer sheet, comprising a substrate sheet and, provided on thesubstrate sheet, a thermally transferable colorant layer of at least onecolor and a thermally transferable protective layer which have beenrepeatedly provided in a face serial manner, is provided and thermaltransfer is carried out onto an object by the thermal transfer meansfor, the formation of an image and the thermal transfer means for theformation of a protective layer in a single thermal transfer printer inan in-line manner.

In the transfer of a protective layer onto an object using the thermaltransfer sheet according to the present invention, a protective layer isformed by transfer onto a thermally transferred image in a predeterminedobject. In this case, registration should be accurately carried out sothat particularly a scratch-resistant layer is located on the thermallytransferred image. To this end, preferably, a method is adopted whereina conventional detection mark for detecting the position in the transferof a protective layers is provided in the thermal transfer sheetaccording to the present invention and is detected with a detector andthis detection is interlocked with a thermal transfer device to registerthe object with the transfer position of the protective layer.

Next, the intermediate transfer recording medium according to thepresent invention will be described.

FIG. 3A is a cross-sectional view showing one embodiment of theintermediate transfer recording medium according to the presentinvention. An intermediate transfer recording medium 301 comprises asubstrate film 302 and a transfer portion 306 provided separably on thesubstrate film 302. The transfer portion 306 comprises a peel layer 303,an ionizing radiation-cured resin layer 304, and a receptive layer 305provided in that order as viewed from the substrate film 302 side.

FIG. 3B is a cross-sectional view showing one embodiment of the printaccording to the present invention. A print 307 comprises an object 309and, provided on the object 309 in the following order, a receptivelayer 305 with a thermally transferred image 308 formed thereon, anionizing radiation-cured resin layer 304, and a release layer 303. Inthis print, a thermally transferred image is previously formed using athermal transfer sheet on the receptive layer in the intermediatetransfer recording medium as shown in FIG. 3A, and, thereafter, thereceptive layer with a thermally transferred image formed thereon, theionizing radiation-cured resin layer, and the release layer aretransferred from the intermediate transfer recording medium onto theobject so that the receptive layer with the image formed thereon comesinto contact with the object, whereby the receptive layer, the ionizingradiation-cured resin layer, and the release layer are stacked on theobject so as to cover the thermally transferred image.

Elements constituting the intermediate transfer recording medium will bedescribed.

Substrate Film:

The substrate film 302 is not particularly limited, and the samesubstrate film as used in the conventional intermediate transferrecording medium as such may be used. Specific examples of preferredsubstrate films 302 include: thin paper, such as glassine paper,capacitor paper, or paraffin-waxed paper; and stretched or unstretchedfilms of plastics, for example, highly heat resistant polyesters, suchas polyethylene terephthalate, polyethylene naphthalate, polybutyleneterephthalate, polyphenylene sulfide, polyether ketone, or polyethersulfone, and other plastics, such as polypropylene, polycarbonate,cellulose acetate, polyethylene derivative, polyvinyl chloride,polyvinylidene chloride, polystyrene, polyamide, polyimide,polymethylpentene, or ionomer. Composite films comprising a laminate oftwo or more materials selected from the above materials may also beused. The thickness of the substrate film 302 may be properly selectedaccording to the material so as to provide proper strength, heatresistance and other properties. In general, however, the thickness ofthe substrate film is preferably about 1 to 100 μm.

If necessary, a backside layer may be provided by a conventional methodon the surface of the substrate film remote from the transfer portion.The backside layer is provided for preventing fusing between thesubstrate film and a heating device, such as a thermal head, at the timeof the transfer of the transfer portion onto the object using theintermediate transfer recording medium to improve the slidability of theintermediate transfer recording medium and may comprise the same resinas used in the prior art.

Peel Layer:

The peel layer 303 generally comprises, for example, a mixture of aresin having an acryl structure, a vinyl chloride-vinyl acetatecopolymer, and a cellulose acetate with a thermosetting acrylic resin, amelamine resin, a nitrocellulose resin, and a polyethylene wax. The useof the resin having an acryl structure as a main component isparticularly preferred. Further, a polyester resin or the like ispreferably used for regulating the adhesion between the peel layer andthe substrate film.

The peel layer may be formed by dissolving or dispersing, for example, aresin having an acryl structure and a polyester resin in a suitablesolvent to prepare a coating liquid for a peel layer, coating thecoating liquid onto a substrate film by gravure printing, screenprinting, reverse coating using a gravure plate or the like, and dryingthe coating. The thickness of the peel layer is generally 0.1 to 10 μmon a dry basis.

Instead of the peel layer, a release layer may be provided on thesubstrate film. The release layer generally comprises a binder resin anda releasable material. Binder resins usable herein include:thermoplastic resins, for example, acrylic resins such as polymethylmethacrylate, polyethyl methacrylate, and polybutyl acrylate, vinylresins such as polyvinyl acetate, vinyl chloride-vinyl acetatecopolymer, polyvinyl alcohol, and polyvinyl butyral, and cellulosederivatives such as ethylcellulose, nitrocellulose, and celluloseacetate; and thermosetting resins such as unsaturated polyester resins,polyester resins, polyurethane resins, and aminoalkyd resins. Releasablematerials include waxes, silicone waxes, silicone resins, melamineresins, fluororesins, finely divided talc or silica, and lubricants suchas surfactants and metallic soaps.

The release layer may be formed by dissolving or dispersing the aboveresin in a suitable solvent to prepare a coating liquid for a releaselayer, coating the coating liquid onto a substrate film by gravureprinting, screen printing, reverse coating using a gravure plate orother method, and drying the coating. The thickness of the release layeris generally 0.1 to 10 μm on a dry basis.

Ionizing Radiation-Cured Resin Layer:

The intermediate transfer recording medium according to the presentinvention comprises a substrate film and a transfer portion provided onthe substrate film. The transfer portion comprises at least a peellayer, an ionizing radiation-cured resin layer, and a receptive layerprovided in that order on the substrate film.

The ionizing radiation-cured resin layer 304 mainly functions to impartvarious fastness and resistance properties to the thermally transferredimage in the transfer portion 306. The ionizing radiation-cured resinlayer is formed from an ionizing radiation-curable resin. The ionizingradiation-curable resin may be the same as used in the thermal transfersheet and may be cured in the same manner as described above to form theionizing radiation-cured resin layer.

The ionizing radiation-curable resin layer may be formed by dissolvingor dispersing a composition containing the ionizing radiation-curableresin for an ionizing radiation-curable resin layer in a suitablesolvent to prepare an ink for the formation of an ionizingradiation-curable resin layer, coating the ink onto the substrate film,for example, by gravure printing, screen printing, reverse coating usinga gravure plate or other means, and drying the coating.

The ionizing radiation-curable resin layer may be formed in any desiredthickness on the substrate film. However, thickness of the ionizingradiation-curable resin layer is 0.1 to 50 g/m², preferably about 1 to20 g/m², on a dry basis.

Receptive Layer:

The receptive layer 305 is provided, as a part of the transfer portionconstituting the intermediate transfer recording medium, so as to belocated at the outermost surface remote from the substrate film. Animage is formed by thermal transfer on the receptive layer from athermal transfer sheet having a colorant layer. The intermediatetransfer recording medium in its transfer portion with the image formedthereon is transferred onto an object, and, thus, a print is formed.

For this reason, a conventional resin material, which is receptive to athermally transferable colorant such as a sublimable dye or a hot-meltink, may be used as the material for the receptive layer. Examples ofmaterials usable herein include: polyolefin resins such aspolypropylene; halogenated resins such as polyvinyl chloride orpolyvinylidene chloride; vinyl resins such as polyvinyl acetate, vinylchloride-vinyl acetate copolymer, ethylene-vinyl acetate copolymer, orpolyacrylic ester; polyester resins such as polyethylene terephthalateor polybutylene terephthalate; polystyrene resin; polyamide resin;resins of copolymers of olefins, such as ethylene or propylene, withother vinyl polymers; ionomers; cellulosic resins such as cellulosediastase; and polycarbonates. Vinyl chloride resins, acryl-styreneresins, or polyester resins are particularly preferred.

When the receptive layer is transferred through an adhesive layer ontoan object, the receptive layer per se is not always required to beadhesive. On the other hand, when the receptive layer is transferredonto the object without through the adhesive layer, the formation of thereceptive layer using a resin material having adhesive properties, suchas vinyl chloride-vinyl acetate copolymer, is preferred.

The receptive layer may be formed by dissolving or dispersing a singleor plurality of materials, selected from the above materials, optionallymixed with various additives or the like, in a suitable solvent such aswater or an organic solvent to prepare a coating liquid for a receptivelayer, coating the coating liquid by means such as gravure printing,screen printing, or reverse coating using a gravure plate, and dryingthe coating. The thickness (coverage) of the receptive layer is about 1to 10 g/m² on a dry basis.

Object:

Next, the object 309 will be described. The intermediate transferrecording medium in its transfer portion with a thermally transferredimage formed thereon is transferred onto the object. This can provide aprint having thereon a thermally transferred image possessing excellentvarious fastness and resistance properties. The object, to which theintermediate transfer recording medium according to the presentinvention is applied, is not particularly limited, and examples thereofinclude natural pulp paper, coated paper, tracing paper, plastic filmswhich are not deformed upon exposure to heat at the time of transfer,glasses, metals, ceramics, wood, and cloths.

Regarding the form and applications of the object, there is nolimitation on the type, and examples thereof include: gold notes, suchas stock certificates, securities, deeds, passbooks, railway tickets,streetcar tickets, stamps, postage stamps, appreciation tickets,admission tickets, and other tickets; cards, such as bank cards, creditcards, prepaid cards, membership cards, greeting cards, postcards,business cards, driver's licenses, IC cards, and optical cards; cases,such as cartons and containers; bags; forms control; envelops; tags; OHPsheets; slide films; bookmarks; calendars; posters; pamphlets; menus;passports; POP goods; coasters; displays; name plates; keyboards;cosmetics; accessories such as wristwatches and lighters; stationeriessuch as report pads; building materials; panels; emblems; keys; cloths;clothes; footwears; equipment or devices such as radios, televisions,electronic calculators, and OA equipment; various sample or patternbooks; albums; and outputs of computer graphics and outputs of medicalimages.

In the formation of a thermally transferred image to produce the printaccording to the present invention, the intermediate transfer recordingmedium and the thermal transfer sheet comprising a colorant layerprovided on a substrate are first provided. The intermediate transferrecording medium and the thermal transfer sheet are sandwiched andpressed between a heating device, such as a thermal head, and a platenroll so that the intermediate transfer recording medium in its transferportion comes into contact with the thermal transfer sheet in itscolorant layer. In this state, heat is selectively generated from theheat generating portion in a heating device according to imageinformation to transfer the colorant in the colorant layer on thethermal transfer sheet onto the receptive layer in the intermediatetransfer recording medium, whereby an image is recorded.

The thermal transfer sheet may be a conventional thermal transfer sheet.The colorant layer provided in the thermal transfer sheet comprises aheat-fusion ink or an ink containing a sublimable dye. The colorantlayer comprises a material properly selected according to a contemplatedprint from heat-fusion inks and sublimable dye inks. A colorant layercomprising sublimable dyes used for producing prints having excellentgradation may be formed by properly providing conventional sublimabledyes, such as yellow, magenta, cyan, and black, in a face serial manneraccording to need. In monochromatic binary images such as characters ornumerals, a thermal transfer sheet comprising a colorant layercomprising a heat-fusion ink possessing excellent density and sharpnessmay be used alone, or alternatively the colorant layer comprising thesublimable dyes and the heat-fusion ink layer may be provided in a faceserial manner.

As described above, a thermally transferred image is formed as a mirrorimage, which is not an image in the final print but an image seen whenthe final image is reflected from a mirror onto the intermediatetransfer recording medium in its transfer portion, and the intermediatetransfer recording medium and an object are pressed so that the imageface in the transfer portion with the thermally transferred image formedthereon comes into contact with the object, followed by transfer of thetransfer portion onto the object by means of heating means such as athermal head, a hot stamp, or a hot roll. Regarding the heating meansfor heating the transfer portion, in the case of a partial transfer, theuse of a thermal head or a hot stamp is preferred, while, in the case oftransfer onto the whole object, the adoption of the hot roll method ispreferred.

Thus, a print is produced wherein the receptive layer and the ionizingradiation-cured resin layer have been stacked onto the object so as tocover the thermally transferred image (see FIG. 3B).

In the formation of the print according to the present invention, atransfer portion including a specified thermally transferred image istransferred onto an object in its specified position. In this case, inorder to accurately perform registration of the position of the thermaltransfer of each color at the time of the thermal transfer of thethermally transferred image, a method is preferably adopted wherein aconventional detection mark for detecting the position in each transferis provided in the intermediate transfer recording medium and isdetected with a detector and this detection is interlocked with athermal transfer device to perform registration for thermal transfer.

EXAMPLES

The present invention will be described in more detail with reference tothe following examples. In the following description, “parts” or “%” isby weight unless otherwise specified.

1: First Thermal Transfer Sheet According to the Present Invention

Example 1A

A 12 μm-thick polyethylene terephthalate film (Lumirror, manufactured byToray Industries, Inc.) was provided as a substrate sheet. A coatingliquid for a peel layer having the following composition was gravurecoated on one side of the substrate sheet to form a peel layer at acoverage of 1.0 g/m² on a dry basis. A coating liquid for ascratch-resistant layer having the following composition was gravurecoated on the peel layer for each picture plane unit as shown in FIG. 1Ato form a scratch-resistant layer at a coverage of 4.0 g/m² on a drybasis. Further, as shown in FIG. 1A, a coating liquid for an adhesivelayer having the following composition was gravure coated on thescratch-resistant layer and the peel layer to form an adhesive layer ata coverage of 1.0 g/m² on a dry basis. Thus, a thermal transfer sheet ofExample 1A was prepared.

After coating of each layer in the thermal transfer sheet, the coatingwas dried by conventional hot-air drying. In the case of thescratch-resistant layer, however, after coating, the coating was driedby hot air and was then exposed to ultraviolet light emitted from anultraviolet exposure system (provided with a high-pressure mercury lamp(output 120 W/cm) using ozone).

A coating liquid for a heat-resistant slip layer having the followingcomposition was previously gravure coated at a coverage of 2.0 g/m² on adry basis onto the other side (backside) of the substrate sheet to formthe heat-resistant slip layer, and, further, after coating, theheat-resistant slip layer was heat aged to cure the coating.

Coating liquid for peel layer: Acrylic resin (methyl methacrylate)   80parts Polyester resin   4 parts Methyl ethyl ketone  100 parts Toluene 100 parts Coating liquid for scratch-resistant layer: Urethane acrylicresin  100 parts Polyfunctional urethane acrylate   20 parts Methylethyl ketone  100 parts Toluene  100 parts Coating liquid for adhesivelayer: Vinyl chloride-vinyl acetate copolymer   20 parts (1000 ALK,manufactured by Denki Kagaku Kogyo K.K.) Methyl ethyl ketone   40 partsToluene   40 parts Coating liquid for heat-resistant slip layer:Polyvinyl butyral resin  3.6 parts (S-lec BX-1, manufactured by SekisuiChemical Co., Ltd.) Polyisocyanate 19.2 parts (Burnock D 750-45,manufactured by Dainippon Ink and Chemicals, Inc.) Phosphate surfactant 2.9 parts (Plysurf A 208 S, manufactured by Dai-Ichi Kogyo Seiyaku Co.,Ltd.) Phosphate surfactant  0.3 part (Phosphanol RD 720, manufactured byToho Chemical Industry Co., Ltd.) Talc (manufactured by Nippon Talc  0.2part Co., Ltd.) Methyl ethyl ketone   33 parts Toluene   33 parts

Example 1B

A thermally transferable protective layer having a layer construction ofpeel layer/scratch-resistant layer/adhesive layer, which is the samelayer construction as adopted in Example 1A, was formed on the samesubstrate sheet as used in the thermal transfer sheet prepared inExample 1A as shown in FIG. 1B. In this case, it is a matter of coursethat, regarding the coating area of each layer in the thermallytransferable protective layer, the scratch-resistant layer was formed ina smaller area than the area of each of the peel layer and the adhesivelayer. The area of the scratch-resistant layer is smaller than the areaof an object in its transfer surface. Further, as shown in FIG. 1B,standard dye layers for a VDS card printer CP 510 were provided asthermally transferable colorant layers of yellow, magenta, and cyan.Thus, a thermal transfer sheet of Example 1B was prepared.

Comparative Example 1A

A thermal transfer sheet of Comparative Example 1A was prepared in thesame manner as in Example 1A, except that, in the preparation of thethermal transfer resin layer in the thermal transfer sheet, a coatingliquid for a thermal transfer resin layer having the followingcomposition was used instead of the coating liquid used in Example 1A.

Coating Liquid for Thermal Transfer Resin Layer:

Polyester resin 20 parts (U-18, manufactured by Arakawa ChemicalIndustries, Ltd.) Methyl ethyl ketone 50 parts Toluene 50 parts

Next, prints for evaluation were provided under the followingconditions.

An object comprising a card substrate having the following compositionwas provided. Further, a thermal printer for cards (a card printer CP510, manufactured by VDS) and a thermal transfer sheet comprisingstandard dye layers for the VDS card printer CP 510 were provided. Thecolor separation of a photograph of a face was carried out, and each dyewas transferred onto the object according to image information onyellow, magenta, and cyan obtained by the color separation to form afull-color photograph-like facial image. For Example 1B, however, sincethe thermal transfer sheet has a thermally transferable colorant layer(dye layer), the thermally transferable colorant layer was used.

Composition of Material for Card Substrate:

Polyvinyl chloride compound (degree of  100 parts polymerization; 800)(content of additives such as stabilizer: about 10%) White pigment(titanium oxide)   10 parts Plasticizer (DOP)  0.5 part

A thermally transferable protective layer was transferred from the abovethermal transfer sheet onto the image in the print so as to cover theimage, as shown in FIG. 1D, by means of the same thermal printer forcards as used above (using the same thermal head as used above).

Results of Evaluation:

Prints, in which the protective layer was transferred, from the thermaltransfer sheets prepared in Examples 1A and 1B, onto the image, hadexcellent various fastness or resistance properties such as excellentlightfastness, chemical resistance, plasticizer resistance, solventresistance, and weathering resistance even when exposed to conditionswhich had simulated very severe service conditions. Further, for thethermal transfer sheets prepared in Examples 1A and 1B, the protectivelayer could be transferred onto the image on the object with goodtransferability. That is, an even protective layer was transferred, andthe edge of the transferred protective layer was linear.

For the thermal transfer sheet prepared in Example 1B wherein thethermally transferable colorant layer and the thermally transferableprotective layer were repeatedly formed in a face serial manner on anidentical substrate sheet, after the formation of an image on theobject, the protective layer could be subsequently transferred onto theimage to prepare a print without the replacement of the thermal transfersheet with another thermal transfer sheet. This saved a lot of time andcould realize the production of a print with high efficiency.

By contrast, the print, in which the protective layer had beentransferred from the thermal transfer sheet prepared in ComparativeExample 1A onto the image, was unsatisfactory in various fastness orresistance properties such as lightfastness, chemical resistance,plasticizer resistance, solvent resistance, and weathering resistancewhen exposed to conditions which had simulated severe serviceconditions.

2: Second Thermal Transfer Sheet According to the Present Invention

Example 2A

A 12 μm-thick polyethylene terephthalate film (Lumirror, manufactured byToray Industries, Inc.) was provided as a substrate sheet. A coatingliquid for a peel layer having the following composition was gravurecoated on one side of the substrate sheet to form a peel layer at acoverage of 1.0 g/m² on a dry basis. A coating liquid for a thermaltransfer resin layer having the following composition was gravure coatedon the peel layer to form a thermal transfer resin layer at a coverageof 4.0 g/m² on a dry basis. Further, a coating liquid for an adhesivelayer having the following composition was gravure coated on the thermaltransfer resin layer to form an adhesive layer at a coverage of 1.0 g/m²on a dry basis. Thus, a thermal transfer sheet of Example 2A wasprepared.

After coating of each layer in the thermal transfer sheet, the coatingwas dried by conventional hot-air drying. In the case of the thermaltransfer resin layer, however, after coating, the coating was dried byhot air and was then exposed to ultraviolet light emitted from anultraviolet exposure system (provided with a high-pressure mercury lamp(output 120 W/cm) using ozone).

A coating liquid for a heat-resistant slip layer having the followingcomposition was previously gravure coated at a coverage of 2.0 g/m² on adry basis onto the other side (backside) of the substrate sheet to formthe heat-resistant slip layer, and, further, after coating, theheat-resistant slip layer was heat aged to cure the coating.

Coating liquid for peel layer: Acrylic resin (methyl methacrylate)   80parts Polyester resin   4 parts Methyl ethyl ketone  100 parts Toluene 100 parts Coating liquid for thermal transfer resin layer: Urethaneacrylic resin  100 parts Polyfunctional urethane acrylate   20 partsMethyl ethyl ketone  100 parts Toluene  100 parts Coating liquid foradhesive layer: Vinyl chloride-vinyl acetate copolymer   20 parts (1000ALK, manufactured by Denki Kagaku Kogyo K.K.) Methyl ethyl ketone   40parts Toluene   40 parts Coating liquid for heat-resistant slip layer:Polyvinyl butyral resin  3.6 parts (S-lec BX-1, manufactured by SekisuiChemical Co., Ltd.) Polyisocyanate 19.2 parts (Burnock D 750-45,manufactured by Dainippon Ink and Chemicals, Inc.) Phosphate surfactant 2.9 parts (Plysurf A 208 S, manufactured by Dai-Ichi Kogyo Seiyaku Co.,Ltd.) Phosphate surfactant  0.3 part (Phosphanol RD 720, manufactured byToho Chemical Industry Co., Ltd.) Talc (manufactured by Nippon Talc  0.2part Co., Ltd.) Methyl ethyl ketone   33 parts Toluene   33 parts

Example 2B

A thermally transferable protective layer having a layer construction ofpeel layer/thermal transfer resin layer/adhesive layer, which is thesame layer construction as adopted in Example 2A, was formed on the samesubstrate sheet as used in the thermal transfer sheet prepared inExample 2A. Further, as shown in FIG. 2B, standard dye layers for a VDScard printer CP 510 were provided as thermally transferable colorantlayers of yellow, magenta, and cyan. Thus, a thermal transfer sheet ofExample 2B was prepared.

Comparative Example 1A

A thermal transfer sheet of Comparative Example 2A was prepared in thesame manner as in Example 2A, except that, in the preparation of thethermal transfer resin layer in the thermal transfer sheet, a coatingliquid for a thermal transfer resin layer having the followingcomposition was used instead of the coating liquid used in Example 2A.

Coating Liquid for Thermal Transfer Resin Layer:

Polyester resin 20 parts (U-18, manufactured by Arakawa ChemicalIndustries, Ltd.). Methyl ethyl ketone 50 parts Toluene 50 parts

Next, prints for evaluation were provided under the followingconditions.

An object comprising a card substrate having the following compositionwas provided. Further, a thermal printer for cards (a card printer CP510, manufactured by VDS) and a thermal transfer sheet comprisingstandard dye layers for the VDS card printer CP 510 were provided. Thecolor separation of a photograph of a face was carried out, and each dyewas transferred onto the object according to image information onyellow, magenta, and cyan obtained by the color separation to form afull-color photograph-like face image. For Example 2B, however, sincethe thermal transfer sheet has a thermally transferable colorant layer(dye layer), the thermally transferable colorant layer was used.

Composition of Material for Card Substrate:

Polyvinyl chloride compound (degree of  100 parts polymerization: 800)(content of additives such as stabilizer: about 10%) White pigment(titanium oxide)   10 parts Plasticizer (DOP)  0.5 part

A thermally transferable protective layer was transferred from the abovethermal transfer sheet onto the image in the print so as to cover theimage, as shown in FIG. 2D, by means of the same thermal printer forcards as used above (using the same thermal head as used above).

Results of Evaluation:

Prints, in which the protective layer was transferred, from the thermaltransfer sheets prepared in Examples 2A and 2B, onto the image, hadexcellent various fastness or resistance properties such as excellentlightfastness, chemical resistance, plasticizer resistance, solventresistance, and weathering resistance even when exposed to conditionswhich had simulated very severe service conditions. Further, for thethermal transfer sheets prepared in Examples 2A and 2B, the protectivelayer could be transferred onto the image on the object with goodtransferability. That is, an even protective layer was transferred, andthe edge of the transferred protective layer was linear.

For the thermal transfer sheet prepared in Example 2B wherein thethermally transferable colorant layer and the thermally transferableprotective layer were repeatedly formed in a face serial manner on anidentical substrate sheet, after the formation of an image on theobject, the protective layer could be subsequently transferred onto theimage to prepare a print without the replacement of the thermal transfersheet with another thermal transfer sheet. This saved a lot of time andcould realize the production of a print with high efficiency.

By contrast, the print, in which the protective layer had beentransferred from the thermal transfer sheet prepared in ComparativeExample 2A onto the image, was unsatisfactory in various fastness orresistance properties such as lightfastness, chemical resistance,plasticizer resistance, solvent resistance, and weathering resistancewhen exposed to conditions which had simulated severe serviceconditions.

3: Intermediate Transfer Recording Medium According to the PresentInvention

Example 3A

A 12 μm-thick transparent polyethylene terephthalate film was firstprovided as a substrate film. A coating liquid for a peel layer havingthe following composition was coated by gravure reverse coating on thesurface of the substrate film, and the coating was dried to form a peellayer at a coverage of 1.0 g/m² on the substrate film.

Coating Liquid for Peel Layer:

Acrylic resin (methyl methacrylate)  80 parts Polyester resin  4 partsMethyl ethyl ketone 100 parts Toluene 100 parts

A coating liquid for an ionizing radiation-curable resin layer havingthe following composition was gravure coated onto the peel layer to forman ionizing radiation-curable resin layer at a coverage of 4.0 g/m² on adry basis. Further, a coating liquid for a receptive layer having thefollowing composition was gravure coated on the cured resin layer toform a receptive layer at a coverage of 2.0 g/m² on a dry basis. Thus,an intermediate transfer recording medium of Example 3A was prepared.

After coating of each layer in the intermediate transfer recordingmedium, the coating was dried by conventional hot-air drying. In thecase of the ionizing radiation-curable resin layer, however, aftercoating, the coating was dried by hot air and was then exposed toultraviolet light emitted from an ultraviolet exposure system (providedwith a high-pressure mercury lamp (output 120 W/cm) using ozone) to forman ionizing radiation-cured resin layer.

A coating liquid for a heat-resistant slip layer having the followingcomposition was previously gravure coated at a coverage of 2.0 g/m² on adry basis onto the other side (backside) of the substrate film to formthe heat-resistant slip layer, and, further, after coating, theheat-resistant slip layer was heat aged to cure the coating.

Coating Liquid for Ionizing Radiation-Curable Resin Layer:

Urethane acrylic resin  100 parts Polyfunctional urethane acrylate   20parts Methyl ethyl ketone  100 parts Toluene  100 partsCoating Liquid for Receptive Layer:

Vinyl chloride-vinyl acetate copolymer   40 parts Acrylic silicone  1.5parts Methyl ethyl ketone   50 parts Toluene   50 partsCoating Liquid for Heat-Resistant Slip Layer:

Polyvinyl butryal resin  3.6 parts (S-lec BX-1, manufactured by SekisuiChemical Co., Ltd.) Polyisocyanate 19.2 parts (Burnock D 750-45,manufactured by Dainippon Ink and Chemicals, Inc.) Phosphate surfactant 2.9 parts (Plysurf A 208 s, manufactured by Dai-Ichi Kogyo Seiyaku Co.,Ltd.) Phosphate surfactant  0.3 part (Phosphanol RD 720, manufactured byToho Chemical Industry Co., Ltd.) Talc (manufactured by Nippon Talc  0.2part Co., Ltd.) Methyl ethyl ketone   33 parts Toluene   33 parts

Comparative Example 3A

An intermediate transfer recording medium of Comparative Example 3A wasprepared in the same manner as in Example 3A, except that a coatingliquid for a thermal transfer resin layer having the followingcomposition was used instead of the coating liquid for the ionizingradiation-curable resin layer in the intermediate transfer recordingmedium.

Coating Liquid for Thermal Transfer Resin Layer:

Polyester resin 20 parts (U-18, manufactured by Arakawa ChemicalIndustries, Ltd.) Methyl ethyl ketone 50 parts Toluene 50 parts

Next, prints for evaluation were provided under the followingconditions.

A thermal printer for cards (a card printer CP 510, manufactured by VDS)and a thermal transfer sheet comprising standard dye layers for the VDScard printer CP 510 were provided. The color separation of a photographof a face was carried out, and each dye was transferred onto thereceptive layer in each of the intermediate transfer recording mediaprepared in the example and comparative example according to imageinformation on yellow, magenta, and cyan to form a full-colorphotograph-like facial image.

The receptive layer including the thermal transfer image and theionizing radiation-cured resin layer (the thermal transfer resin layerin the comparative example) were transferred onto an object comprising acard substrate having the following composition by means of the samethermal printer for cards as used above (using the same thermal head asused above).

Composition of Material for Card Substrate:

Polyvinyl chloride compound (degree of  100 parts polymerization: 800)(content of additives such as stabilizer: about 10%) White pigment(titanium oxide)   10 parts Plasticizer (DOP)  0.5 partResults of Evaluation:

Prints, in which the ionizing radiation-cured resin layer formed inExample 3A was provided on the image, had excellent various fastness orresistance properties such as excellent lightfastness, chemicalresistance, plasticizer resistance, solvent resistance, and weatheringresistance even when exposed to conditions which had simulated verysevere service conditions. Further, for the intermediate transferrecording medium prepared in Example 3A, the transfer portion could betransferred onto the object with good transferability. That is, thetransfer portion could be evenly transferred, and the edge of thetransferred transfer portion was sharp.

By contrast, the print, in which the resin layer formed in ComparativeExample 3A was provided on the image, was unsatisfactory in variousfastness or resistance properties such as lightfastness, chemicalresistance, plasticizer resistance, solvent resistance, and weatheringresistance when exposed to conditions which had simulated severe serviceconditions.

1. A thermal transfer sheet comprising a substrate sheet and a thermallytransferable protective layer provided on the substrate sheet, whereinthe thermally transferable protective layer comprises ascratch-resistant layer, the scratch-resistant layer is repeatedlyprovided one by one for each picture plane unit in the thermal transfersheet, and an area of the scratch-resistant layer for each picture planeunit is smaller than an area of an object in its transfer surface. 2.The thermal transfer sheet according to claim 1, wherein the thermallytransferable protective layer comprises a peel layer, thescratch-resistant layer, and an adhesive layer provided in that order asviewed from the substrate sheet side.
 3. The thermal transfer sheetaccording to claim 2, wherein the scratch-resistant layer comprises acured product of an ionizing radiation-curable resin.
 4. The thermaltransfer sheet according to claim 3, wherein the ionizingradiation-curable resin comprises urethane-modified acrylic base resin.5. The thermal transfer sheet according to claim 3, wherein the ionizingradiation-curable resin further comprises 5 to 40 parts by weight, basedon 100 parts by weight of the urethane-modified acrylic base resin, ofan oligomer.
 6. A thermal transfer sheet according to claim 1, wherein athermally transferable colorant layer(s) for at least one color isprovided on the substrate sheet, the thermally transferable protectivelayer is then provided on the substrate sheet so that the thermallytransferable colorant layer and the thermally transferable protectivelayer constitute one picture plane unit, and a combination of thethermally transferable colorant layer with the thermally transferableprotective layer is repeatedly provided for constituting each pictureplane unit.
 7. A thermal transfer sheet comprising a substrate sheet anda thermally transferable protective layer provided on the substratesheet, wherein the thermally transferable protective layer comprises atleast a peel layer, a thermal transfer resin layer, and an adhesivelayer provided in that order as viewed from the substrate sheet side,and the thermal transfer resin layer comprises a cured product of anionizing radiation-curable resin.
 8. A thermal transfer sheet accordingto claim 7, wherein a thermally transferable colorant layer(s) for atleast one color is provided on the substrate sheet, the thermallytransferable protective layer is then provided on the substrate sheet sothat the thermally transferable colorant layer and the thermallytransferable protective layer constitute one picture plane unit, and acombination of the thermally transferable colorant layer with thethermally transferable protective layer is repeatedly provided forconstituting each picture plane unit.
 9. The thermal transfer sheetaccording to claim 7, wherein the ionizing radiation-curable resincomprises a urethane-modified acrylic base resin.
 10. The thermaltransfer sheet according to claim 7, wherein the ionizingradiation-curable resin further comprises 5 to 40 parts by weight, basedon 100 parts by weight of the urethane-modified acrylic base resin, ofan oligomer.